The present invention relates to an apparatus for determining optical properties of liquid samples. More particularly, but not exclusively, the invention relates to an apparatus for carrying out tests pertaining to chemical chemistry, enzyme immuno assays (EIA), enzyme linked immunosorbent assays (ELISA) and turbidimetric assays for example.
Various optical arrangements are known for measuring and analysing biological/chemical test samples. For example, conventional spectrophotometers are available commercially, but such instruments are typically bulky, not inexpensive and require a high degree of operator skill or specialisation. Various automated analysis systems of the kind described in U.S. Pat. No. 3,770,382 and U.S. Pat. No. 3,897,216 are also known, in which the sample cells are transported sequentially through a test station on a conveyor chain during the course of a test operation. Such systems are typically large and complex in design and are correspondingly expensive. Further, optical density measuring apparatuses of the kind described in U.S. Pat. No. 4,729,661 are known in which the specimens are contained within a cuvette tray and movement of the cuvette tray through a test station is effected by translating the tray along an open channel defined in and along the front edge of the chassis of the apparatus.
In the above-mentioned prior art devices, sample cells are passed sequentially through a beam of light and the light signal transmitted therethrough is then detected and processed. Typically the sample cells are in the form of expensive microcuvettes having optical quality faces to ensure that test results are not degraded by imperfections in the sample containers. The prior art devices also commonly have had to employ a number of light sources to ensure that a sufficiently high level of light intensity is produced over a broad spectral band of wavelengths. For example, special-design light bulbs have had to be employed to perform measurements in the ultraviolet waveband. In the known devices, it is also difficult to position or locate accurately the sample(s) with respect to the light beam which adds an unwanted uncertainty to each measurement.
The aim of the present invention is to provide an improved apparatus which overcomes or substantially reduces at least some of the above-discussed drawbacks and limitations.
According to the present invention there is provided an apparatus for determining optical properties of liquid samples held in transparent containers, said apparatus comprising:
means defining a mounting for a plurality of said containers in a linear array;
an optical head mounted for translation along the length of said array, said optical head including a light source on one side of the array, a light detector on the other side of the array for detecting light from the source after it has passed through the array, and means defining an optical path between the source and the detector such that in use of the apparatus the light from the source scans across the liquid samples as the head is moved; and
means responsive to the output of said light detector during translation of the head along the length of the array for determining the optical properties of each of the samples in the array.
A housing of the apparatus is advantageously provided with an opening at its upper surface for receiving a carrier which defines the mounting for the containers in the linear array. The array may be in the form of a rectilinear array, and the optical head may be arranged so as to move rectilinearly.
The housing of the apparatus and the carrier may be configured so as to inhibit the passage of extraneous light through the housing opening when the carrier is inserted.
Further, the optical head may be mounted on a carriage, or alternatively, the optical head may comprise a carriage. The carriage is, advantageously, engaged with one or more guide rails in the apparatus to permit movement of the optical head/carriage along the length of the rails. The carriage may also comprise linear bearing means which ensures easy movement of the optical head/carriage along the rail(s). Advantageously, the carriage includes spaced-apart wheels adapted to run on a support track provided in the apparatus. The wheels may be configured so as to produce a (sufficient) reaction force which biases the carriage into firm contact with the rail(s).
Furthermore, the apparatus may include an electric drive motor coupled to the carriage by means of a drive belt. The electric drive motor is preferably in the form of a reversible stepper motor. The drive belt is preferably in the form of a toothed belt. Such an arrangement enables a controlled movement of the optical head past the array of samples and also enables a corresponding controlled analysis of the output of the light detector for each sample.
The apparatus may provide means for supplying pulsatory drive signals to the drive motor and means for correlating the output of the detector with the positions of the samples in the array.
The apparatus may provide processor means for controlling the application of drive signals to the motor and for effecting sampling of the detector output, thereby identifying in the detector output that signal portion which corresponds to each of the samples. The processing means may also be arranged to effect a curve fitting algorithm upon the signal portions associated with the separate samples. Such a curve fitting algorithm may be structured to take no account of glitches in the signal portions corresponding to imperfections in the containers. In addition, the processing means may be arranged to derive a weighted average of the signal portions associated with the samples. This kind of processing advantageously enables high precision, reproducible measurements to be made on test samples contained in simple test tubes as opposed to in expensive microcuvettes.
The optical head may preferably comprise a solid block (for example, made of aluminium alloy) defining a mounting for the light source, a mounting for the light detector and a recess for the passage of containers through the optical head when the head is moved during operation of the apparatus. The provision of such a block head limits unwanted aberrations in the optical path and inhibits the passage of extraneous light through the apparatus. Further, the provision of a moving head past the samples permits the apparatus to be in a compact, portable form. The apparatus may, for example, fit into a briefcase.
Advantageously, the optical head may include a filter carrier (for example, a filter wheel system) having a plurality of different bandpass or interference filters mounted therein. The apparatus may also be adapted and arranged to introduce automatically the requisite filter into the optical path.
Preferably, the apparatus may include a bar code reader for entering information into the apparatus so as to condition the apparatus for the performance of specific optical property tests.
The apparatus may further include means for adjusting the power supplied to the or each said light source so as to determine the optimum spectral output and/or the intensity thereof. Standard tungsten-halogen bulbs with a quartz envelope may, for example, be employed to perform measurements in the ultraviolet waveband.
The apparatus may be used to carry out numerous routine and speciality laboratory tests quickly and to a high precision. Use of the apparatus does not require a high degree of operator skill or specialisation. The apparatus may be mains-operated or operated from batteries.
The above and further features of the present invention are set forth in the appended claims and, together with advantages thereof, will become more clear from consideration of the following detailed description of exemplary embodiments of the invention given with reference to the accompanying drawings.